Could be a bad driver from Windows update. Try running in safe mode for a while. Easiest way to get to it ( if you've not enabled F8) is press the SHIFT key and click on any power icon, select 'restart' still pressing the Shift key. You should then get the Advanced Option blue screen. Select Troubleshoot - advanced options - Start-up settings - restart - from the list select safe mode with networking. It should go online if not using an adapter. See if it runs ok. If it does check windows update and see if the graphics driver has been updated. My guess is it could be that.
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